The present invention relates to a color filter used in a liquid crystal display device or an imaging device and a method of manufacturing the same. Also, the invention relates to a photosensitive coloring composition used in the manufacture of the color filter.
A color filter used in a color liquid crystal display device or an imaging device is generally manufactured by forming pixels of the three primary colors, red, green and blue, on a transparent substrate of glass or the like. Furthermore, a light-shielding layer, a black matrix, is generally formed for shielding light between these pixels. In forming colored pixels by using a photosensitive coloring composition, the photosensitive coloring composition containing a pigment corresponding to each color is uniformly applied on a transparent substrate bearing a pattern of a light-shielding layer with a spin coater or the like, and the resultant is dried by heating (pre-bake). Then, the thus formed coat film is exposed, developed and subjected to post-curing (post-bake). These procedures are repeated with respect to each color necessary for the color filter, resulting in forming pixels of all the colors.
A generally used light-shielding layer has a single layer structure of chromium or a multilayer structure having a chromium layer exposed on the surface and a chromium oxide layer. On a transparent glass substrate bearing such a light-shielding layer, pixels of the colors necessary for a color filter are formed as described above. There is, however, a problem that a development residue mainly derived from a pigment remains on the light-shielding layer and the transparent substrate after development. Such a development residue remaining on the light-shielding layer degrades adhesion between an ITO (transparent electrode) or an over coat (a flattening layer for the color filter), which is stacked on the color filter after forming colored pixels, and the substrate. This development residue also causes peeling on the interface. On the other hand, a development residue remaining on the transparent substrate degrades the color reproducibility because pixels of respective colors are successively formed in the manufacture of the color filter.
In order to remove such a development residue, various methods have been examined. A method for treating with a liquid containing hydrofluoric acid as described in JP-A-5-224014 is known as an improvement process for attaining the purpose. A method for using a specific nonionic surfactant as described in JP-A-8-286387 and a method for using an alkaline aqueous solution including a specific amine and a nonionic surfactant as described in JP-A-8-292487 are proposed for attaining the purpose by an improvement of developper.
Such improvement from the viewpoints of processes and a developer, however, cannot sufficiently remove a development residue. Furthermore, the improvement processes increases cost.
For the purpose of improving disperse stability of a pigment, JP-A-7-306530 discloses a photosensitive solution containing an organic solvent and a disperse resin having an acid value of 20 through 300 mg KOH/g so that the solution obtained by dissolving the disperse resin in the organic solvent can attain viscosity within a specific range. For the purpose of improving photosensitivity and disperse stability of a pigment, JP-A-7-319161 discloses a photosensitive solution that contains a disperse resin having an acid value of 20 through 300 mg KOH/g and an unsaturated equivalent of 600 through 3,000 and has thixotropy within a specific range. In these publications, a development residue remaining after development is not particularly considered. According to examination made by the present inventors, the amount of a development residue cannot be effectively reduced under conditions described in these publications.
Problems to be Solved by the Invention
The present inventors have conducted extensive studies in order to solve the problems of the conventional techniques for reducing the amount of a development residue generated in the manufacture of a color filter. As a result, it was found that the acid value of a nonvolatile component of a photosensitive coloring composition used for forming colored pixels affects the amount of a development residue, and that the amount of a development residue remaining on a light-shielding layer and a transparent portion on a substrate after development can be remarkably reduced by using a composition in which the acid value is adjusted. Thus, the present invention was completed.
An object of the present invention is to provide a color filter in which a minimal amount of development residue remains on a light-shielding layer and a transparent portion on a substrate after development, which can be produced by using a specific photosensitive coloring composition. Another object of the present invention is to provide such a photosensitive coloring composition used for producing a color filter capable of reducing the amount of development residue remaining on a light-shielding layer and a transparent portion on a substrate after development.
The present invention provides a color filter which comprises a transparent substrate, a light-shielding layer patterned thereon and colored pixels of plural colors patterned on a portion of the substrate where the light-shielding layer is not formed, wherein the colored pixels of at least one color are formed from a photosensitive coloring composition comprising (A) a pigment; (B) a copolymer of (meth)acrylic acid, as one monomer, and at least one other monomer; (C) a photopolymerizable monomer; (D) a photopolymerization initiator; and (F) a solvent, and the acid value of a nonvolatile component of the photosensitive coloring composition is 25 through 60 mg KOH/g. After forming the colored pixels from a photosensitive coloring composition, the light-shielding layer attains reflectance at 380 through 780 nm of 95% or more of reflectance thereof before coating the photosensitive coloring composition; and the transparent portion of the substrate attains transmittance at 380 through 780 nm of 99.5% or more of transmittance thereof before coating the photosensitive coloring composition.
This color filter is manufactured by coating the photosensitive coloring composition on the transparent substrate bearing the light-shielding layer, drying the thus obtained coat film, irradiating the coat film with light through a mask and developing the coat film so as to form the colored pixels. The present invention also provides a photosensitive coloring composition comprising (A) a pigment; (B) a copolymer of (meth)acrylic acid, as one monomer, and at least one other monomer; (C) a photopolymerizable monomer; (D) a photopolymerization initiator; and (F) a solvent, in which an acid value of a nonvolatile component of the photosensitive coloring composition is 25 through 60 mg KOH/g. After forming colored pixels by coating the composition on a transparent substrate bearing a light-shielding layer, drying the coat film and subjecting the dried coat film to pattern exposure and alkaline development, the light-shielding layer attains reflectance at 380 through 780 nm of 95% or more of reflectance thereof before coating the composition, and a transparent portion of the substrate attains transmittance at 380 through 780 nm of 99.5% or more of transmittance thereof before coating the composition.